The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Internal combustion engines combust an air and fuel mixture within cylinders to drive pistons. The reciprocating movement of the pistons produces drive torque. Air is regulated and drawn into an intake manifold through a throttle. Fuel is injected by fuel injectors and the amount of injected fuel depends on a duration the fuel injectors are energized. Air and fuel are mixed outside or in combustion chambers of the cylinders to create an air and fuel mixture.
The air/fuel ratio of the mixture is controlled to meet different engine demands. For example, the engine may demand a stoichiometric air/fuel mixture (i.e., an air/fuel ratio of 14.7 for gasoline engines) in light load cruise situations. The engine may demand a rich air/fuel mixture (i.e., an air/fuel ratio less than 14.7 for gasoline engines) during cold start conditions.
The air/fuel ratio of the mixture in different cylinders, however, may vary due to different delivery rates of the injectors along a fuel rail. Due to manufacturing tolerances, the “same” injectors along the fuel rail may not deliver the same amount of fuel for a desired duration the injectors are open. The amount of fuel injected by the “same” injectors may vary by as much as ±5%, resulting in cylinder-to-cylinder air/fuel imbalance.